image for How I fixed my mountain lion battery issues on a macbook air 2012
How I fixed my mountain lion battery issues on a macbook air 2012

How I fixed my mountain lion battery issues on a macbook air 2012

I upgraded from lion to mountain lion on my Macbook air 2012.
Instantly I noticed that the battery life was terrible.
Instead of 8 -9 hours I was getting 2-3 hours. under the same load.

I looked round the apple forums, and didn’t find anything.
I found a post somewhere [sorry, can't remember where] that suggested I delete the desktop preferences plist file and restart the Dock.

It seems to have worked for me.
I now have 8 hours battery life again.

To apply this fix:
open terminal

rm ~/Library/Preferences/com.apple.desktop.plist
killall Dock

You will lose your wallpaper settings, but your battery life should be fixed.

Please let me know in the comments if it works, and I might be able to get some evidence to send to apple for a fix!

UPDATE:
Some nice people from Reddit came along, and some of them said that it isn’t a fix.

I thought id put my reasoning in here incase you need convincing.

my guess is that its something to do with mission control or launchpad, though I did notice in the plist file itself that there is a
Change = Never;
ChangeTime = 1800;
if the change = never is getting ignored, and the ChangeTime is seconds, then every 30 mins each of your desktops refresh. probably not enough to have an impact on your battery, but if its ms, then every 1.8 seconds its refreshing.
that would be enough to kill your battery.

deleting the file resets it to have pretty much nothing in it. which seems to fit with my fix

Update 2: Apple have released a couple of firmware updates for Macbook air and Macbook pro that might help
  • Matthew

    Library/Preferences/com.desktop.plist: No such file or directory

    The battery life on my macbook pro is fine after upgrading to OSX Mountain Lion. Could it be specific to new macbook air?

    • http://jonathansblog.co.uk jonathan

      its ~/Library/Preferences/com.desktop.plist
      [the library file in your users home folder]

      not /Library/Preferences/com.desktop.plist
      there are two library folders.i think its loads of macbook pro retinas and macbook airs that have the problem, i dont think its the old style macbook pros though
      here is a [currently] 27 page thread about it on apples forums https://discussions.apple.com/thread/4135250?start=120&tstart=0

  • http://www.facebook.com/timothy.vickery Tim Vickery

    Seemed to help me a bit, but the proper path for me was ~/Library/Preferences/com.apple.desktop.plist — no com.desktop.plist existed. Thanks for posting.

    • http://jonathansblog.co.uk jonathan

      cool, post fixed :)

  • http://www.facebook.com/joshua.j.lucero Joshua Lucero

    Seems to have fixed my battery life problem for the time being on my mid-2012 air. Back up to about 7 hrs from the 4 it was getting right after the ML install.

  • Mike McAdams

    Hey guys, I’m trying to run the ~/Library/Preferences/com.apple.desktop.plist command in terminal and getting permission denied…. am I missing a step? Thanks for the help; working with significantly reduced battery life on my 2011 Macbook Air.

    • http://jonathansblog.co.uk jonathan

      in the terminal you will have to type
      rm ~/Library/Preferences/com.apple.desktop.plist
      the rm stands for ‘remove’

  • Javi

    will this work on a pro?

    • http://jonathansblog.co.uk jonathan

      not sure, but it might work!
      let us know uf it helps :D

  • http://www.facebook.com/people/Jim-Tardiff/1137319371 Jim Tardiff

    I tried this on my MBA 2012, and it definitely has increased my battery life. Once I upgraded to Mt. Lion, my batter life dropped to about 3.5hrs. After, I did this little command, its back up around 7.5hr -8hrs. I haven’t let it cycle down, but its definitely holding a better charge life.

  • http://twitter.com/maksa maksa

    Worked for me as well. Amazing. Thank you Sir.

    Being a programmer, I’m dying to learn how exactly did this affect battery life.

    • Josh

      Unlike windows, Apples desktop takes notice of all the items sitting there. More items equal more memory.. im guessing theres something monitoring all of this and causing the same with a process or something.

  • http://twitter.com/jennajennjenn Jenna Furr

    It doesn’t seem to work on my macbook air. Can anyone help?

  • Manish Mandhyan

    Did not work for me. Have a MBA mid 2012. Battery life still about 3.5-4hrs.

  • http://twitter.com/Keith_Walker Keith Walker

    I have no experience of using Terminal, but trusted your advice and battery performance (on my 17in MBP) has returned to levels I saw prior to ML install. Thank you sir

  • Jake

    Thanks for this great fix! Does anyone know if restarting your computer brings the problem back, or is this a one-time fix?

    • http://twitter.com/mikerhodes09 Mike Rhodes

      Got a more permanent fix. Make an automator application, place the code lines above into a shell-script box and save the app anywhere. Then go to; System Prefs. > Users. Click on your account and toggle to login items. Now drag the automator app to this list. Now every time you login, these codes will run automatically and hopefully solve the battery problem until there’s an official patch.

  • Thanks, Apple :P

    2012 MBA 11″ – with Lion I had 5h+ battery life. “Upgraded” yesterday, left it connected all day yesterday and all night just to make sure it runs Spotlight indexing and such. Disconnected this morning, seeing 1h45 battery estimate. Currently at 81% (1h27) after ~15 minutes of use. 7 minutes later, everything except Safari closed and it’s showing 2h14min battery life. Seems to have improved somewhat but still far from what it used to be. If this doesn’t solve it I’m throwing ML away and not coming back. This is just sad. (and now it’s dropping down again, 1 minute later I have 2h04min left… so my Air is now officially useless.)

  • Michael

    Just like some others above I had no experience with terminal but after following your advice my battery life has almost doubled on my MBP late 2011 back to the same as with Lion! I was just about to re-install Lion so thanks a lot :-)

  • Izzy

    It definitely increased battery life for me. I was seeing 4.5 hours before the fix, after i did the command, it’s showing 6 hours and 23 minutes. I think this fix did it for me. Im on a 2011 Macbook Air if that helps.

  • Alvin

    It didnt change it much. All i did was open terminal and copy and paste the following: “rm ~/Library/Preferences/com.apple.desktop.plis” i have a mid 2011 MBP 13in. I cant stand that the battery is only at 3.5 hours…a far cry from 8.5 hours before loading OSX ML. Did I do this right?

  • Wences García

    It worked for me, thank you!

  • Ville

    This did not fix problem for me.

    Changetime is not a refresh interval and it is in seconds. You can change this setting in System Preferences. It is used to change desktop image when not set to “never”.

    So the problem have to be something else in this pref file? I also noticed that after resetting desktop settings I had an Illustrator-file as a wallpaper by mistake. Never had an idea that they would work that way. I’ll change that to png file and try change other wallpaper settings.

    I also have this time setting two times in .plist file. Interesting.

  • http://twitter.com/atomicattack Calvin Ho

    Could someone tell me if I did something wrong? I have the MBP Retina 15″. I had 4 hours left in a 100% charged battery. Then I jjust copied both lines “rm ~/Library/Preferences/com.apple.desktop.plist” and then “killall Dock” but nothing seems to happen, the hours left of battery life is the same. Can someone actually make it work on the same MBP retina? Thanks

  • rohit m

    hey, i think your fix is working. Thanks in advance :)

  • http://twitter.com/mikerhodes09 Mike Rhodes

    It’s working for me. I had 5 hours on a full charge. After executing those codes in terminal and waiting a few mins my battery shot up to 9.5 hours on idle! It doesn’t seem to be a permanent fix. After restarting my MBA (mid 2012), it went back to 5 hours until I executed the code again. May see if I can make something on automator to put in the codes for me every time I turn on my mac.

  • Adi

    Hi. it did not work for me. I just updated from Lion to Mountain Lion and my battery reduced to almost half. Could someone please help me get my battery life back?? Thanks.
    I am using Aug 2010 MacBook Pro if that helps.

  • Apez

    It most certainly worked for me! My 100% charge went from 2.5 to 7 hours! I am super pleased and glad I am one of the lucky ones.